The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Substrate processing systems may be used to etch film on a substrate such as a semiconductor wafer. The substrate processing systems typically include a processing chamber, a gas distribution device and a substrate support. Examples of substrate processing systems for etching include transformer coupled plasma (TCP), inductive coupled plasma (ICP) and capacitively coupled plasma (CCP) systems.
During processing, the substrate is arranged on the substrate support. Different gas mixtures may be introduced into the processing chamber and radio frequency (RF) plasma may be used to activate chemical reactions. In some semiconductor manufacturing processes, several types of film may be exposed during an etching step. Normally, the etching process etches the various types of film at the same or similar etching rates.
Some semiconductor manufacturing processes may require one type of film on a substrate to be etched more than other types of film on the substrate. This type of etching is called selective etching since the etching process etches one film with little or no removal or damage to one or more other types of film. Highly selective etching is very desirable for some steps of the semiconductor manufacturing process. Examples of film that may need to be etched selectively include silicon nitride (SiN), polysilicon, pure silicon and silicon dioxide (SiO2).